The essential problem to be solved on this type of seeder is the problem of seed selection by the distributor where the apertured disk should only carry one seed per aperture. The solution of this problem lies with both the acquisition of the seeds by the suction apertures in the distributor disk and also at the member for rejecting the double seeds, hereinafter called selector, with which the modern seeders are equipped.
In a known single-seed seeder, as described in particular in French Pat. No. 1,208,202, gripping of the seeds by the suction apertures in the distributor disk is facilitated by a stirring action exerted by a stirrer when the blades rotate in parallel relationship to the disk. Solution is effected by adjustable paddles, positioned in a staggered arrangement on both sides of the path of the seeds carried by the distributor, said paddles defining said path. Selection is also effected by alternately joggling the packs of seeds acquired by the suction apertures towards the center of the disk and towards the periphery thereof. This selection system fails to be completely satisfactory in as much as the stirrer does not push the seeds towards the disk, but drive them in a direction parallel to the latter. Also, joggling the packs of seeds acquired by the suction apertures once in each direction, is in some cases insufficient.
On another improved single-seed seeder machine, described in particular in French Pat. No. 1,585,445, seed stirring in the reservoir adjacent to the carrier disk is also effected in a direction parallel to the disk, but the adjustable selection paddles of the previous seeder were replaced by a selector plate with saw-teeth so as to form a plurality of successive slanted ramps such that the saw teeth are gradually closer together in relation to the path of the suction apertures in the distributor disk. With this device, the packs of seeds caked onto the suction apertures are subjected to a series of successive impacts which cause the packs to revolve on themselves and bring forth the fall of the excessive seeds. While being satisfactory, it will be noted that with this selector plate, the seed packs are only pushed in a single radial direction, either towards the center of the distributor disk, or on the contrary, towards the periphery thereof, which may give advantage to some seeds located in a privileged position within the pack acquired by the suction aperture.